IL-20 is expressed in PsA and RA synovial tissues. (A) Representative immunohistochemical staining of baseline IL-20 expression in synovial tissue from PsA and RA patients. Arrows indicate expression of IL-20 in both lining and sublining. (B) Quantification of IL-20 expression in RA and PsA synovial tissues. Results are shown as median IOD (integrated optical density)/mm2 × 105 of 10 patients with RA and 11 patients with PsA. (C) Double-immunohistochemistry stainings of IL-20 (red) and CD68+ macrophages (blue) and CD55+ FLS (blue) in PsA synovium. A representative double immunostaining of PsA synovium from one patient is shown. Arrows indicate double-positive cells. Original magnification, ×200. CRP, C-reactive protein; DAS28, disease activity score; ESR, erythrocyte sedimentation rate; SJC, swollen-joint count; TJC, tender-joint count; VAS, visual analogue scale (100 mm).